1/* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7/* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14#include <linux/slab.h> 15#include <linux/init.h> 16#include <linux/unistd.h> 17#include <linux/module.h> 18#include <linux/vmalloc.h> 19#include <linux/completion.h> 20#include <linux/personality.h> 21#include <linux/mempolicy.h> 22#include <linux/sem.h> 23#include <linux/file.h> 24#include <linux/fdtable.h> 25#include <linux/iocontext.h> 26#include <linux/key.h> 27#include <linux/binfmts.h> 28#include <linux/mman.h> 29#include <linux/mmu_notifier.h> 30#include <linux/fs.h> 31#include <linux/mm.h> 32#include <linux/vmacache.h> 33#include <linux/nsproxy.h> 34#include <linux/capability.h> 35#include <linux/cpu.h> 36#include <linux/cgroup.h> 37#include <linux/security.h> 38#include <linux/hugetlb.h> 39#include <linux/seccomp.h> 40#include <linux/swap.h> 41#include <linux/syscalls.h> 42#include <linux/jiffies.h> 43#include <linux/futex.h> 44#include <linux/compat.h> 45#include <linux/kthread.h> 46#include <linux/task_io_accounting_ops.h> 47#include <linux/rcupdate.h> 48#include <linux/ptrace.h> 49#include <linux/mount.h> 50#include <linux/audit.h> 51#include <linux/memcontrol.h> 52#include <linux/ftrace.h> 53#include <linux/proc_fs.h> 54#include <linux/profile.h> 55#include <linux/rmap.h> 56#include <linux/ksm.h> 57#include <linux/acct.h> 58#include <linux/tsacct_kern.h> 59#include <linux/cn_proc.h> 60#include <linux/freezer.h> 61#include <linux/delayacct.h> 62#include <linux/taskstats_kern.h> 63#include <linux/random.h> 64#include <linux/tty.h> 65#include <linux/blkdev.h> 66#include <linux/fs_struct.h> 67#include <linux/magic.h> 68#include <linux/perf_event.h> 69#include <linux/posix-timers.h> 70#include <linux/user-return-notifier.h> 71#include <linux/oom.h> 72#include <linux/khugepaged.h> 73#include <linux/signalfd.h> 74#include <linux/uprobes.h> 75#include <linux/aio.h> 76#include <linux/compiler.h> 77#include <linux/sysctl.h> 78 79#include <asm/pgtable.h> 80#include <asm/pgalloc.h> 81#include <asm/uaccess.h> 82#include <asm/mmu_context.h> 83#include <asm/cacheflush.h> 84#include <asm/tlbflush.h> 85 86#include <trace/events/sched.h> 87 88#define CREATE_TRACE_POINTS 89#include <trace/events/task.h> 90 91/* 92 * Minimum number of threads to boot the kernel 93 */ 94#define MIN_THREADS 20 95 96/* 97 * Maximum number of threads 98 */ 99#define MAX_THREADS FUTEX_TID_MASK 100 101/* 102 * Protected counters by write_lock_irq(&tasklist_lock) 103 */ 104unsigned long total_forks; /* Handle normal Linux uptimes. */ 105int nr_threads; /* The idle threads do not count.. */ 106 107int max_threads; /* tunable limit on nr_threads */ 108 109DEFINE_PER_CPU(unsigned long, process_counts) = 0; 110 111__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 112 113#ifdef CONFIG_PROVE_RCU 114int lockdep_tasklist_lock_is_held(void) 115{ 116 return lockdep_is_held(&tasklist_lock); 117} 118EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 119#endif /* #ifdef CONFIG_PROVE_RCU */ 120 121int nr_processes(void) 122{ 123 int cpu; 124 int total = 0; 125 126 for_each_possible_cpu(cpu) 127 total += per_cpu(process_counts, cpu); 128 129 return total; 130} 131 132void __weak arch_release_task_struct(struct task_struct *tsk) 133{ 134} 135 136#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 137static struct kmem_cache *task_struct_cachep; 138 139static inline struct task_struct *alloc_task_struct_node(int node) 140{ 141 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 142} 143 144static inline void free_task_struct(struct task_struct *tsk) 145{ 146 kmem_cache_free(task_struct_cachep, tsk); 147} 148#endif 149 150void __weak arch_release_thread_info(struct thread_info *ti) 151{ 152} 153 154#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 155 156/* 157 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 158 * kmemcache based allocator. 159 */ 160# if THREAD_SIZE >= PAGE_SIZE 161static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 162 int node) 163{ 164 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP, 165 THREAD_SIZE_ORDER); 166 167 return page ? page_address(page) : NULL; 168} 169 170static inline void free_thread_info(struct thread_info *ti) 171{ 172 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER); 173} 174# else 175static struct kmem_cache *thread_info_cache; 176 177static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 178 int node) 179{ 180 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 181} 182 183static void free_thread_info(struct thread_info *ti) 184{ 185 kmem_cache_free(thread_info_cache, ti); 186} 187 188void thread_info_cache_init(void) 189{ 190 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 191 THREAD_SIZE, 0, NULL); 192 BUG_ON(thread_info_cache == NULL); 193} 194# endif 195#endif 196 197/* SLAB cache for signal_struct structures (tsk->signal) */ 198static struct kmem_cache *signal_cachep; 199 200/* SLAB cache for sighand_struct structures (tsk->sighand) */ 201struct kmem_cache *sighand_cachep; 202 203/* SLAB cache for files_struct structures (tsk->files) */ 204struct kmem_cache *files_cachep; 205 206/* SLAB cache for fs_struct structures (tsk->fs) */ 207struct kmem_cache *fs_cachep; 208 209/* SLAB cache for vm_area_struct structures */ 210struct kmem_cache *vm_area_cachep; 211 212/* SLAB cache for mm_struct structures (tsk->mm) */ 213static struct kmem_cache *mm_cachep; 214 215static void account_kernel_stack(struct thread_info *ti, int account) 216{ 217 struct zone *zone = page_zone(virt_to_page(ti)); 218 219 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 220} 221 222void free_task(struct task_struct *tsk) 223{ 224 account_kernel_stack(tsk->stack, -1); 225 arch_release_thread_info(tsk->stack); 226 free_thread_info(tsk->stack); 227 rt_mutex_debug_task_free(tsk); 228 ftrace_graph_exit_task(tsk); 229 put_seccomp_filter(tsk); 230 arch_release_task_struct(tsk); 231 free_task_struct(tsk); 232} 233EXPORT_SYMBOL(free_task); 234 235static inline void free_signal_struct(struct signal_struct *sig) 236{ 237 taskstats_tgid_free(sig); 238 sched_autogroup_exit(sig); 239 kmem_cache_free(signal_cachep, sig); 240} 241 242static inline void put_signal_struct(struct signal_struct *sig) 243{ 244 if (atomic_dec_and_test(&sig->sigcnt)) 245 free_signal_struct(sig); 246} 247 248void __put_task_struct(struct task_struct *tsk) 249{ 250 WARN_ON(!tsk->exit_state); 251 WARN_ON(atomic_read(&tsk->usage)); 252 WARN_ON(tsk == current); 253 254 task_numa_free(tsk); 255 security_task_free(tsk); 256 exit_creds(tsk); 257 delayacct_tsk_free(tsk); 258 put_signal_struct(tsk->signal); 259 260 if (!profile_handoff_task(tsk)) 261 free_task(tsk); 262} 263EXPORT_SYMBOL_GPL(__put_task_struct); 264 265void __init __weak arch_task_cache_init(void) { } 266 267/* 268 * set_max_threads 269 */ 270static void set_max_threads(unsigned int max_threads_suggested) 271{ 272 u64 threads; 273 274 /* 275 * The number of threads shall be limited such that the thread 276 * structures may only consume a small part of the available memory. 277 */ 278 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 279 threads = MAX_THREADS; 280 else 281 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 282 (u64) THREAD_SIZE * 8UL); 283 284 if (threads > max_threads_suggested) 285 threads = max_threads_suggested; 286 287 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 288} 289 290void __init fork_init(void) 291{ 292#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 293#ifndef ARCH_MIN_TASKALIGN 294#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 295#endif 296 /* create a slab on which task_structs can be allocated */ 297 task_struct_cachep = 298 kmem_cache_create("task_struct", sizeof(struct task_struct), 299 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 300#endif 301 302 /* do the arch specific task caches init */ 303 arch_task_cache_init(); 304 305 set_max_threads(MAX_THREADS); 306 307 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 308 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 309 init_task.signal->rlim[RLIMIT_SIGPENDING] = 310 init_task.signal->rlim[RLIMIT_NPROC]; 311} 312 313int __weak arch_dup_task_struct(struct task_struct *dst, 314 struct task_struct *src) 315{ 316 *dst = *src; 317 return 0; 318} 319 320void set_task_stack_end_magic(struct task_struct *tsk) 321{ 322 unsigned long *stackend; 323 324 stackend = end_of_stack(tsk); 325 *stackend = STACK_END_MAGIC; /* for overflow detection */ 326} 327 328static struct task_struct *dup_task_struct(struct task_struct *orig) 329{ 330 struct task_struct *tsk; 331 struct thread_info *ti; 332 int node = tsk_fork_get_node(orig); 333 int err; 334 335 tsk = alloc_task_struct_node(node); 336 if (!tsk) 337 return NULL; 338 339 ti = alloc_thread_info_node(tsk, node); 340 if (!ti) 341 goto free_tsk; 342 343 err = arch_dup_task_struct(tsk, orig); 344 if (err) 345 goto free_ti; 346 347 tsk->stack = ti; 348#ifdef CONFIG_SECCOMP 349 /* 350 * We must handle setting up seccomp filters once we're under 351 * the sighand lock in case orig has changed between now and 352 * then. Until then, filter must be NULL to avoid messing up 353 * the usage counts on the error path calling free_task. 354 */ 355 tsk->seccomp.filter = NULL; 356#endif 357 358 setup_thread_stack(tsk, orig); 359 clear_user_return_notifier(tsk); 360 clear_tsk_need_resched(tsk); 361 set_task_stack_end_magic(tsk); 362 363#ifdef CONFIG_CC_STACKPROTECTOR 364 tsk->stack_canary = get_random_int(); 365#endif 366 367 /* 368 * One for us, one for whoever does the "release_task()" (usually 369 * parent) 370 */ 371 atomic_set(&tsk->usage, 2); 372#ifdef CONFIG_BLK_DEV_IO_TRACE 373 tsk->btrace_seq = 0; 374#endif 375 tsk->splice_pipe = NULL; 376 tsk->task_frag.page = NULL; 377 378 account_kernel_stack(ti, 1); 379 380 return tsk; 381 382free_ti: 383 free_thread_info(ti); 384free_tsk: 385 free_task_struct(tsk); 386 return NULL; 387} 388 389#ifdef CONFIG_MMU 390static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 391{ 392 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 393 struct rb_node **rb_link, *rb_parent; 394 int retval; 395 unsigned long charge; 396 397 uprobe_start_dup_mmap(); 398 down_write(&oldmm->mmap_sem); 399 flush_cache_dup_mm(oldmm); 400 uprobe_dup_mmap(oldmm, mm); 401 /* 402 * Not linked in yet - no deadlock potential: 403 */ 404 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 405 406 /* No ordering required: file already has been exposed. */ 407 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 408 409 mm->total_vm = oldmm->total_vm; 410 mm->shared_vm = oldmm->shared_vm; 411 mm->exec_vm = oldmm->exec_vm; 412 mm->stack_vm = oldmm->stack_vm; 413 414 rb_link = &mm->mm_rb.rb_node; 415 rb_parent = NULL; 416 pprev = &mm->mmap; 417 retval = ksm_fork(mm, oldmm); 418 if (retval) 419 goto out; 420 retval = khugepaged_fork(mm, oldmm); 421 if (retval) 422 goto out; 423 424 prev = NULL; 425 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 426 struct file *file; 427 428 if (mpnt->vm_flags & VM_DONTCOPY) { 429 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 430 -vma_pages(mpnt)); 431 continue; 432 } 433 charge = 0; 434 if (mpnt->vm_flags & VM_ACCOUNT) { 435 unsigned long len = vma_pages(mpnt); 436 437 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 438 goto fail_nomem; 439 charge = len; 440 } 441 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 442 if (!tmp) 443 goto fail_nomem; 444 *tmp = *mpnt; 445 INIT_LIST_HEAD(&tmp->anon_vma_chain); 446 retval = vma_dup_policy(mpnt, tmp); 447 if (retval) 448 goto fail_nomem_policy; 449 tmp->vm_mm = mm; 450 if (anon_vma_fork(tmp, mpnt)) 451 goto fail_nomem_anon_vma_fork; 452 tmp->vm_flags &= ~VM_LOCKED; 453 tmp->vm_next = tmp->vm_prev = NULL; 454 file = tmp->vm_file; 455 if (file) { 456 struct inode *inode = file_inode(file); 457 struct address_space *mapping = file->f_mapping; 458 459 get_file(file); 460 if (tmp->vm_flags & VM_DENYWRITE) 461 atomic_dec(&inode->i_writecount); 462 i_mmap_lock_write(mapping); 463 if (tmp->vm_flags & VM_SHARED) 464 atomic_inc(&mapping->i_mmap_writable); 465 flush_dcache_mmap_lock(mapping); 466 /* insert tmp into the share list, just after mpnt */ 467 vma_interval_tree_insert_after(tmp, mpnt, 468 &mapping->i_mmap); 469 flush_dcache_mmap_unlock(mapping); 470 i_mmap_unlock_write(mapping); 471 } 472 473 /* 474 * Clear hugetlb-related page reserves for children. This only 475 * affects MAP_PRIVATE mappings. Faults generated by the child 476 * are not guaranteed to succeed, even if read-only 477 */ 478 if (is_vm_hugetlb_page(tmp)) 479 reset_vma_resv_huge_pages(tmp); 480 481 /* 482 * Link in the new vma and copy the page table entries. 483 */ 484 *pprev = tmp; 485 pprev = &tmp->vm_next; 486 tmp->vm_prev = prev; 487 prev = tmp; 488 489 __vma_link_rb(mm, tmp, rb_link, rb_parent); 490 rb_link = &tmp->vm_rb.rb_right; 491 rb_parent = &tmp->vm_rb; 492 493 mm->map_count++; 494 retval = copy_page_range(mm, oldmm, mpnt); 495 496 if (tmp->vm_ops && tmp->vm_ops->open) 497 tmp->vm_ops->open(tmp); 498 499 if (retval) 500 goto out; 501 } 502 /* a new mm has just been created */ 503 arch_dup_mmap(oldmm, mm); 504 retval = 0; 505out: 506 up_write(&mm->mmap_sem); 507 flush_tlb_mm(oldmm); 508 up_write(&oldmm->mmap_sem); 509 uprobe_end_dup_mmap(); 510 return retval; 511fail_nomem_anon_vma_fork: 512 mpol_put(vma_policy(tmp)); 513fail_nomem_policy: 514 kmem_cache_free(vm_area_cachep, tmp); 515fail_nomem: 516 retval = -ENOMEM; 517 vm_unacct_memory(charge); 518 goto out; 519} 520 521static inline int mm_alloc_pgd(struct mm_struct *mm) 522{ 523 mm->pgd = pgd_alloc(mm); 524 if (unlikely(!mm->pgd)) 525 return -ENOMEM; 526 return 0; 527} 528 529static inline void mm_free_pgd(struct mm_struct *mm) 530{ 531 pgd_free(mm, mm->pgd); 532} 533#else 534static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 535{ 536 down_write(&oldmm->mmap_sem); 537 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 538 up_write(&oldmm->mmap_sem); 539 return 0; 540} 541#define mm_alloc_pgd(mm) (0) 542#define mm_free_pgd(mm) 543#endif /* CONFIG_MMU */ 544 545__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 546 547#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 548#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 549 550static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 551 552static int __init coredump_filter_setup(char *s) 553{ 554 default_dump_filter = 555 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 556 MMF_DUMP_FILTER_MASK; 557 return 1; 558} 559 560__setup("coredump_filter=", coredump_filter_setup); 561 562#include <linux/init_task.h> 563 564static void mm_init_aio(struct mm_struct *mm) 565{ 566#ifdef CONFIG_AIO 567 spin_lock_init(&mm->ioctx_lock); 568 mm->ioctx_table = NULL; 569#endif 570} 571 572static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 573{ 574#ifdef CONFIG_MEMCG 575 mm->owner = p; 576#endif 577} 578 579static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 580{ 581 mm->mmap = NULL; 582 mm->mm_rb = RB_ROOT; 583 mm->vmacache_seqnum = 0; 584 atomic_set(&mm->mm_users, 1); 585 atomic_set(&mm->mm_count, 1); 586 init_rwsem(&mm->mmap_sem); 587 INIT_LIST_HEAD(&mm->mmlist); 588 mm->core_state = NULL; 589 atomic_long_set(&mm->nr_ptes, 0); 590 mm_nr_pmds_init(mm); 591 mm->map_count = 0; 592 mm->locked_vm = 0; 593 mm->pinned_vm = 0; 594 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 595 spin_lock_init(&mm->page_table_lock); 596 mm_init_cpumask(mm); 597 mm_init_aio(mm); 598 mm_init_owner(mm, p); 599 mmu_notifier_mm_init(mm); 600 clear_tlb_flush_pending(mm); 601#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 602 mm->pmd_huge_pte = NULL; 603#endif 604 605 if (current->mm) { 606 mm->flags = current->mm->flags & MMF_INIT_MASK; 607 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 608 } else { 609 mm->flags = default_dump_filter; 610 mm->def_flags = 0; 611 } 612 613 if (mm_alloc_pgd(mm)) 614 goto fail_nopgd; 615 616 if (init_new_context(p, mm)) 617 goto fail_nocontext; 618 619 return mm; 620 621fail_nocontext: 622 mm_free_pgd(mm); 623fail_nopgd: 624 free_mm(mm); 625 return NULL; 626} 627 628static void check_mm(struct mm_struct *mm) 629{ 630 int i; 631 632 for (i = 0; i < NR_MM_COUNTERS; i++) { 633 long x = atomic_long_read(&mm->rss_stat.count[i]); 634 635 if (unlikely(x)) 636 printk(KERN_ALERT "BUG: Bad rss-counter state " 637 "mm:%p idx:%d val:%ld\n", mm, i, x); 638 } 639 640 if (atomic_long_read(&mm->nr_ptes)) 641 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 642 atomic_long_read(&mm->nr_ptes)); 643 if (mm_nr_pmds(mm)) 644 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 645 mm_nr_pmds(mm)); 646 647#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 648 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 649#endif 650} 651 652/* 653 * Allocate and initialize an mm_struct. 654 */ 655struct mm_struct *mm_alloc(void) 656{ 657 struct mm_struct *mm; 658 659 mm = allocate_mm(); 660 if (!mm) 661 return NULL; 662 663 memset(mm, 0, sizeof(*mm)); 664 return mm_init(mm, current); 665} 666 667/* 668 * Called when the last reference to the mm 669 * is dropped: either by a lazy thread or by 670 * mmput. Free the page directory and the mm. 671 */ 672void __mmdrop(struct mm_struct *mm) 673{ 674 BUG_ON(mm == &init_mm); 675 mm_free_pgd(mm); 676 destroy_context(mm); 677 mmu_notifier_mm_destroy(mm); 678 check_mm(mm); 679 free_mm(mm); 680} 681EXPORT_SYMBOL_GPL(__mmdrop); 682 683/* 684 * Decrement the use count and release all resources for an mm. 685 */ 686void mmput(struct mm_struct *mm) 687{ 688 might_sleep(); 689 690 if (atomic_dec_and_test(&mm->mm_users)) { 691 uprobe_clear_state(mm); 692 exit_aio(mm); 693 ksm_exit(mm); 694 khugepaged_exit(mm); /* must run before exit_mmap */ 695 exit_mmap(mm); 696 set_mm_exe_file(mm, NULL); 697 if (!list_empty(&mm->mmlist)) { 698 spin_lock(&mmlist_lock); 699 list_del(&mm->mmlist); 700 spin_unlock(&mmlist_lock); 701 } 702 if (mm->binfmt) 703 module_put(mm->binfmt->module); 704 mmdrop(mm); 705 } 706} 707EXPORT_SYMBOL_GPL(mmput); 708 709/** 710 * set_mm_exe_file - change a reference to the mm's executable file 711 * 712 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 713 * 714 * Main users are mmput() and sys_execve(). Callers prevent concurrent 715 * invocations: in mmput() nobody alive left, in execve task is single 716 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 717 * mm->exe_file, but does so without using set_mm_exe_file() in order 718 * to do avoid the need for any locks. 719 */ 720void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 721{ 722 struct file *old_exe_file; 723 724 /* 725 * It is safe to dereference the exe_file without RCU as 726 * this function is only called if nobody else can access 727 * this mm -- see comment above for justification. 728 */ 729 old_exe_file = rcu_dereference_raw(mm->exe_file); 730 731 if (new_exe_file) 732 get_file(new_exe_file); 733 rcu_assign_pointer(mm->exe_file, new_exe_file); 734 if (old_exe_file) 735 fput(old_exe_file); 736} 737 738/** 739 * get_mm_exe_file - acquire a reference to the mm's executable file 740 * 741 * Returns %NULL if mm has no associated executable file. 742 * User must release file via fput(). 743 */ 744struct file *get_mm_exe_file(struct mm_struct *mm) 745{ 746 struct file *exe_file; 747 748 rcu_read_lock(); 749 exe_file = rcu_dereference(mm->exe_file); 750 if (exe_file && !get_file_rcu(exe_file)) 751 exe_file = NULL; 752 rcu_read_unlock(); 753 return exe_file; 754} 755EXPORT_SYMBOL(get_mm_exe_file); 756 757/** 758 * get_task_mm - acquire a reference to the task's mm 759 * 760 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 761 * this kernel workthread has transiently adopted a user mm with use_mm, 762 * to do its AIO) is not set and if so returns a reference to it, after 763 * bumping up the use count. User must release the mm via mmput() 764 * after use. Typically used by /proc and ptrace. 765 */ 766struct mm_struct *get_task_mm(struct task_struct *task) 767{ 768 struct mm_struct *mm; 769 770 task_lock(task); 771 mm = task->mm; 772 if (mm) { 773 if (task->flags & PF_KTHREAD) 774 mm = NULL; 775 else 776 atomic_inc(&mm->mm_users); 777 } 778 task_unlock(task); 779 return mm; 780} 781EXPORT_SYMBOL_GPL(get_task_mm); 782 783struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 784{ 785 struct mm_struct *mm; 786 int err; 787 788 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 789 if (err) 790 return ERR_PTR(err); 791 792 mm = get_task_mm(task); 793 if (mm && mm != current->mm && 794 !ptrace_may_access(task, mode)) { 795 mmput(mm); 796 mm = ERR_PTR(-EACCES); 797 } 798 mutex_unlock(&task->signal->cred_guard_mutex); 799 800 return mm; 801} 802 803static void complete_vfork_done(struct task_struct *tsk) 804{ 805 struct completion *vfork; 806 807 task_lock(tsk); 808 vfork = tsk->vfork_done; 809 if (likely(vfork)) { 810 tsk->vfork_done = NULL; 811 complete(vfork); 812 } 813 task_unlock(tsk); 814} 815 816static int wait_for_vfork_done(struct task_struct *child, 817 struct completion *vfork) 818{ 819 int killed; 820 821 freezer_do_not_count(); 822 killed = wait_for_completion_killable(vfork); 823 freezer_count(); 824 825 if (killed) { 826 task_lock(child); 827 child->vfork_done = NULL; 828 task_unlock(child); 829 } 830 831 put_task_struct(child); 832 return killed; 833} 834 835/* Please note the differences between mmput and mm_release. 836 * mmput is called whenever we stop holding onto a mm_struct, 837 * error success whatever. 838 * 839 * mm_release is called after a mm_struct has been removed 840 * from the current process. 841 * 842 * This difference is important for error handling, when we 843 * only half set up a mm_struct for a new process and need to restore 844 * the old one. Because we mmput the new mm_struct before 845 * restoring the old one. . . 846 * Eric Biederman 10 January 1998 847 */ 848void mm_release(struct task_struct *tsk, struct mm_struct *mm) 849{ 850 /* Get rid of any futexes when releasing the mm */ 851#ifdef CONFIG_FUTEX 852 if (unlikely(tsk->robust_list)) { 853 exit_robust_list(tsk); 854 tsk->robust_list = NULL; 855 } 856#ifdef CONFIG_COMPAT 857 if (unlikely(tsk->compat_robust_list)) { 858 compat_exit_robust_list(tsk); 859 tsk->compat_robust_list = NULL; 860 } 861#endif 862 if (unlikely(!list_empty(&tsk->pi_state_list))) 863 exit_pi_state_list(tsk); 864#endif 865 866 uprobe_free_utask(tsk); 867 868 /* Get rid of any cached register state */ 869 deactivate_mm(tsk, mm); 870 871 /* 872 * If we're exiting normally, clear a user-space tid field if 873 * requested. We leave this alone when dying by signal, to leave 874 * the value intact in a core dump, and to save the unnecessary 875 * trouble, say, a killed vfork parent shouldn't touch this mm. 876 * Userland only wants this done for a sys_exit. 877 */ 878 if (tsk->clear_child_tid) { 879 if (!(tsk->flags & PF_SIGNALED) && 880 atomic_read(&mm->mm_users) > 1) { 881 /* 882 * We don't check the error code - if userspace has 883 * not set up a proper pointer then tough luck. 884 */ 885 put_user(0, tsk->clear_child_tid); 886 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 887 1, NULL, NULL, 0); 888 } 889 tsk->clear_child_tid = NULL; 890 } 891 892 /* 893 * All done, finally we can wake up parent and return this mm to him. 894 * Also kthread_stop() uses this completion for synchronization. 895 */ 896 if (tsk->vfork_done) 897 complete_vfork_done(tsk); 898} 899 900/* 901 * Allocate a new mm structure and copy contents from the 902 * mm structure of the passed in task structure. 903 */ 904static struct mm_struct *dup_mm(struct task_struct *tsk) 905{ 906 struct mm_struct *mm, *oldmm = current->mm; 907 int err; 908 909 mm = allocate_mm(); 910 if (!mm) 911 goto fail_nomem; 912 913 memcpy(mm, oldmm, sizeof(*mm)); 914 915 if (!mm_init(mm, tsk)) 916 goto fail_nomem; 917 918 err = dup_mmap(mm, oldmm); 919 if (err) 920 goto free_pt; 921 922 mm->hiwater_rss = get_mm_rss(mm); 923 mm->hiwater_vm = mm->total_vm; 924 925 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 926 goto free_pt; 927 928 return mm; 929 930free_pt: 931 /* don't put binfmt in mmput, we haven't got module yet */ 932 mm->binfmt = NULL; 933 mmput(mm); 934 935fail_nomem: 936 return NULL; 937} 938 939static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 940{ 941 struct mm_struct *mm, *oldmm; 942 int retval; 943 944 tsk->min_flt = tsk->maj_flt = 0; 945 tsk->nvcsw = tsk->nivcsw = 0; 946#ifdef CONFIG_DETECT_HUNG_TASK 947 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 948#endif 949 950 tsk->mm = NULL; 951 tsk->active_mm = NULL; 952 953 /* 954 * Are we cloning a kernel thread? 955 * 956 * We need to steal a active VM for that.. 957 */ 958 oldmm = current->mm; 959 if (!oldmm) 960 return 0; 961 962 /* initialize the new vmacache entries */ 963 vmacache_flush(tsk); 964 965 if (clone_flags & CLONE_VM) { 966 atomic_inc(&oldmm->mm_users); 967 mm = oldmm; 968 goto good_mm; 969 } 970 971 retval = -ENOMEM; 972 mm = dup_mm(tsk); 973 if (!mm) 974 goto fail_nomem; 975 976good_mm: 977 tsk->mm = mm; 978 tsk->active_mm = mm; 979 return 0; 980 981fail_nomem: 982 return retval; 983} 984 985static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 986{ 987 struct fs_struct *fs = current->fs; 988 if (clone_flags & CLONE_FS) { 989 /* tsk->fs is already what we want */ 990 spin_lock(&fs->lock); 991 if (fs->in_exec) { 992 spin_unlock(&fs->lock); 993 return -EAGAIN; 994 } 995 fs->users++; 996 spin_unlock(&fs->lock); 997 return 0; 998 } 999 tsk->fs = copy_fs_struct(fs); 1000 if (!tsk->fs) 1001 return -ENOMEM; 1002 return 0; 1003} 1004 1005static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1006{ 1007 struct files_struct *oldf, *newf; 1008 int error = 0; 1009 1010 /* 1011 * A background process may not have any files ... 1012 */ 1013 oldf = current->files; 1014 if (!oldf) 1015 goto out; 1016 1017 if (clone_flags & CLONE_FILES) { 1018 atomic_inc(&oldf->count); 1019 goto out; 1020 } 1021 1022 newf = dup_fd(oldf, &error); 1023 if (!newf) 1024 goto out; 1025 1026 tsk->files = newf; 1027 error = 0; 1028out: 1029 return error; 1030} 1031 1032static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1033{ 1034#ifdef CONFIG_BLOCK 1035 struct io_context *ioc = current->io_context; 1036 struct io_context *new_ioc; 1037 1038 if (!ioc) 1039 return 0; 1040 /* 1041 * Share io context with parent, if CLONE_IO is set 1042 */ 1043 if (clone_flags & CLONE_IO) { 1044 ioc_task_link(ioc); 1045 tsk->io_context = ioc; 1046 } else if (ioprio_valid(ioc->ioprio)) { 1047 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1048 if (unlikely(!new_ioc)) 1049 return -ENOMEM; 1050 1051 new_ioc->ioprio = ioc->ioprio; 1052 put_io_context(new_ioc); 1053 } 1054#endif 1055 return 0; 1056} 1057 1058static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1059{ 1060 struct sighand_struct *sig; 1061 1062 if (clone_flags & CLONE_SIGHAND) { 1063 atomic_inc(¤t->sighand->count); 1064 return 0; 1065 } 1066 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1067 rcu_assign_pointer(tsk->sighand, sig); 1068 if (!sig) 1069 return -ENOMEM; 1070 atomic_set(&sig->count, 1); 1071 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1072 return 0; 1073} 1074 1075void __cleanup_sighand(struct sighand_struct *sighand) 1076{ 1077 if (atomic_dec_and_test(&sighand->count)) { 1078 signalfd_cleanup(sighand); 1079 /* 1080 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1081 * without an RCU grace period, see __lock_task_sighand(). 1082 */ 1083 kmem_cache_free(sighand_cachep, sighand); 1084 } 1085} 1086 1087/* 1088 * Initialize POSIX timer handling for a thread group. 1089 */ 1090static void posix_cpu_timers_init_group(struct signal_struct *sig) 1091{ 1092 unsigned long cpu_limit; 1093 1094 /* Thread group counters. */ 1095 thread_group_cputime_init(sig); 1096 1097 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1098 if (cpu_limit != RLIM_INFINITY) { 1099 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1100 sig->cputimer.running = 1; 1101 } 1102 1103 /* The timer lists. */ 1104 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1105 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1106 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1107} 1108 1109static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1110{ 1111 struct signal_struct *sig; 1112 1113 if (clone_flags & CLONE_THREAD) 1114 return 0; 1115 1116 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1117 tsk->signal = sig; 1118 if (!sig) 1119 return -ENOMEM; 1120 1121 sig->nr_threads = 1; 1122 atomic_set(&sig->live, 1); 1123 atomic_set(&sig->sigcnt, 1); 1124 1125 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1126 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1127 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1128 1129 init_waitqueue_head(&sig->wait_chldexit); 1130 sig->curr_target = tsk; 1131 init_sigpending(&sig->shared_pending); 1132 INIT_LIST_HEAD(&sig->posix_timers); 1133 seqlock_init(&sig->stats_lock); 1134 1135 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1136 sig->real_timer.function = it_real_fn; 1137 1138 task_lock(current->group_leader); 1139 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1140 task_unlock(current->group_leader); 1141 1142 posix_cpu_timers_init_group(sig); 1143 1144 tty_audit_fork(sig); 1145 sched_autogroup_fork(sig); 1146 1147#ifdef CONFIG_CGROUPS 1148 init_rwsem(&sig->group_rwsem); 1149#endif 1150 1151 sig->oom_score_adj = current->signal->oom_score_adj; 1152 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1153 1154 sig->has_child_subreaper = current->signal->has_child_subreaper || 1155 current->signal->is_child_subreaper; 1156 1157 mutex_init(&sig->cred_guard_mutex); 1158 1159 return 0; 1160} 1161 1162static void copy_seccomp(struct task_struct *p) 1163{ 1164#ifdef CONFIG_SECCOMP 1165 /* 1166 * Must be called with sighand->lock held, which is common to 1167 * all threads in the group. Holding cred_guard_mutex is not 1168 * needed because this new task is not yet running and cannot 1169 * be racing exec. 1170 */ 1171 assert_spin_locked(¤t->sighand->siglock); 1172 1173 /* Ref-count the new filter user, and assign it. */ 1174 get_seccomp_filter(current); 1175 p->seccomp = current->seccomp; 1176 1177 /* 1178 * Explicitly enable no_new_privs here in case it got set 1179 * between the task_struct being duplicated and holding the 1180 * sighand lock. The seccomp state and nnp must be in sync. 1181 */ 1182 if (task_no_new_privs(current)) 1183 task_set_no_new_privs(p); 1184 1185 /* 1186 * If the parent gained a seccomp mode after copying thread 1187 * flags and between before we held the sighand lock, we have 1188 * to manually enable the seccomp thread flag here. 1189 */ 1190 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1191 set_tsk_thread_flag(p, TIF_SECCOMP); 1192#endif 1193} 1194 1195SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1196{ 1197 current->clear_child_tid = tidptr; 1198 1199 return task_pid_vnr(current); 1200} 1201 1202static void rt_mutex_init_task(struct task_struct *p) 1203{ 1204 raw_spin_lock_init(&p->pi_lock); 1205#ifdef CONFIG_RT_MUTEXES 1206 p->pi_waiters = RB_ROOT; 1207 p->pi_waiters_leftmost = NULL; 1208 p->pi_blocked_on = NULL; 1209#endif 1210} 1211 1212/* 1213 * Initialize POSIX timer handling for a single task. 1214 */ 1215static void posix_cpu_timers_init(struct task_struct *tsk) 1216{ 1217 tsk->cputime_expires.prof_exp = 0; 1218 tsk->cputime_expires.virt_exp = 0; 1219 tsk->cputime_expires.sched_exp = 0; 1220 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1221 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1222 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1223} 1224 1225static inline void 1226init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1227{ 1228 task->pids[type].pid = pid; 1229} 1230 1231/* 1232 * This creates a new process as a copy of the old one, 1233 * but does not actually start it yet. 1234 * 1235 * It copies the registers, and all the appropriate 1236 * parts of the process environment (as per the clone 1237 * flags). The actual kick-off is left to the caller. 1238 */ 1239static struct task_struct *copy_process(unsigned long clone_flags, 1240 unsigned long stack_start, 1241 unsigned long stack_size, 1242 int __user *child_tidptr, 1243 struct pid *pid, 1244 int trace) 1245{ 1246 int retval; 1247 struct task_struct *p; 1248 1249 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1250 return ERR_PTR(-EINVAL); 1251 1252 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1253 return ERR_PTR(-EINVAL); 1254 1255 /* 1256 * Thread groups must share signals as well, and detached threads 1257 * can only be started up within the thread group. 1258 */ 1259 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1260 return ERR_PTR(-EINVAL); 1261 1262 /* 1263 * Shared signal handlers imply shared VM. By way of the above, 1264 * thread groups also imply shared VM. Blocking this case allows 1265 * for various simplifications in other code. 1266 */ 1267 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1268 return ERR_PTR(-EINVAL); 1269 1270 /* 1271 * Siblings of global init remain as zombies on exit since they are 1272 * not reaped by their parent (swapper). To solve this and to avoid 1273 * multi-rooted process trees, prevent global and container-inits 1274 * from creating siblings. 1275 */ 1276 if ((clone_flags & CLONE_PARENT) && 1277 current->signal->flags & SIGNAL_UNKILLABLE) 1278 return ERR_PTR(-EINVAL); 1279 1280 /* 1281 * If the new process will be in a different pid or user namespace 1282 * do not allow it to share a thread group or signal handlers or 1283 * parent with the forking task. 1284 */ 1285 if (clone_flags & CLONE_SIGHAND) { 1286 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1287 (task_active_pid_ns(current) != 1288 current->nsproxy->pid_ns_for_children)) 1289 return ERR_PTR(-EINVAL); 1290 } 1291 1292 retval = security_task_create(clone_flags); 1293 if (retval) 1294 goto fork_out; 1295 1296 retval = -ENOMEM; 1297 p = dup_task_struct(current); 1298 if (!p) 1299 goto fork_out; 1300 1301 ftrace_graph_init_task(p); 1302 1303 rt_mutex_init_task(p); 1304 1305#ifdef CONFIG_PROVE_LOCKING 1306 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1307 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1308#endif 1309 retval = -EAGAIN; 1310 if (atomic_read(&p->real_cred->user->processes) >= 1311 task_rlimit(p, RLIMIT_NPROC)) { 1312 if (p->real_cred->user != INIT_USER && 1313 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1314 goto bad_fork_free; 1315 } 1316 current->flags &= ~PF_NPROC_EXCEEDED; 1317 1318 retval = copy_creds(p, clone_flags); 1319 if (retval < 0) 1320 goto bad_fork_free; 1321 1322 /* 1323 * If multiple threads are within copy_process(), then this check 1324 * triggers too late. This doesn't hurt, the check is only there 1325 * to stop root fork bombs. 1326 */ 1327 retval = -EAGAIN; 1328 if (nr_threads >= max_threads) 1329 goto bad_fork_cleanup_count; 1330 1331 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1332 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1333 p->flags |= PF_FORKNOEXEC; 1334 INIT_LIST_HEAD(&p->children); 1335 INIT_LIST_HEAD(&p->sibling); 1336 rcu_copy_process(p); 1337 p->vfork_done = NULL; 1338 spin_lock_init(&p->alloc_lock); 1339 1340 init_sigpending(&p->pending); 1341 1342 p->utime = p->stime = p->gtime = 0; 1343 p->utimescaled = p->stimescaled = 0; 1344#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE 1345 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1346#endif 1347#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1348 seqlock_init(&p->vtime_seqlock); 1349 p->vtime_snap = 0; 1350 p->vtime_snap_whence = VTIME_SLEEPING; 1351#endif 1352 1353#if defined(SPLIT_RSS_COUNTING) 1354 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1355#endif 1356 1357 p->default_timer_slack_ns = current->timer_slack_ns; 1358 1359 task_io_accounting_init(&p->ioac); 1360 acct_clear_integrals(p); 1361 1362 posix_cpu_timers_init(p); 1363 1364 p->start_time = ktime_get_ns(); 1365 p->real_start_time = ktime_get_boot_ns(); 1366 p->io_context = NULL; 1367 p->audit_context = NULL; 1368 if (clone_flags & CLONE_THREAD) 1369 threadgroup_change_begin(current); 1370 cgroup_fork(p); 1371#ifdef CONFIG_NUMA 1372 p->mempolicy = mpol_dup(p->mempolicy); 1373 if (IS_ERR(p->mempolicy)) { 1374 retval = PTR_ERR(p->mempolicy); 1375 p->mempolicy = NULL; 1376 goto bad_fork_cleanup_threadgroup_lock; 1377 } 1378#endif 1379#ifdef CONFIG_CPUSETS 1380 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1381 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1382 seqcount_init(&p->mems_allowed_seq); 1383#endif 1384#ifdef CONFIG_TRACE_IRQFLAGS 1385 p->irq_events = 0; 1386 p->hardirqs_enabled = 0; 1387 p->hardirq_enable_ip = 0; 1388 p->hardirq_enable_event = 0; 1389 p->hardirq_disable_ip = _THIS_IP_; 1390 p->hardirq_disable_event = 0; 1391 p->softirqs_enabled = 1; 1392 p->softirq_enable_ip = _THIS_IP_; 1393 p->softirq_enable_event = 0; 1394 p->softirq_disable_ip = 0; 1395 p->softirq_disable_event = 0; 1396 p->hardirq_context = 0; 1397 p->softirq_context = 0; 1398#endif 1399#ifdef CONFIG_LOCKDEP 1400 p->lockdep_depth = 0; /* no locks held yet */ 1401 p->curr_chain_key = 0; 1402 p->lockdep_recursion = 0; 1403#endif 1404 1405#ifdef CONFIG_DEBUG_MUTEXES 1406 p->blocked_on = NULL; /* not blocked yet */ 1407#endif 1408#ifdef CONFIG_BCACHE 1409 p->sequential_io = 0; 1410 p->sequential_io_avg = 0; 1411#endif 1412 1413 /* Perform scheduler related setup. Assign this task to a CPU. */ 1414 retval = sched_fork(clone_flags, p); 1415 if (retval) 1416 goto bad_fork_cleanup_policy; 1417 1418 retval = perf_event_init_task(p); 1419 if (retval) 1420 goto bad_fork_cleanup_policy; 1421 retval = audit_alloc(p); 1422 if (retval) 1423 goto bad_fork_cleanup_perf; 1424 /* copy all the process information */ 1425 shm_init_task(p); 1426 retval = copy_semundo(clone_flags, p); 1427 if (retval) 1428 goto bad_fork_cleanup_audit; 1429 retval = copy_files(clone_flags, p); 1430 if (retval) 1431 goto bad_fork_cleanup_semundo; 1432 retval = copy_fs(clone_flags, p); 1433 if (retval) 1434 goto bad_fork_cleanup_files; 1435 retval = copy_sighand(clone_flags, p); 1436 if (retval) 1437 goto bad_fork_cleanup_fs; 1438 retval = copy_signal(clone_flags, p); 1439 if (retval) 1440 goto bad_fork_cleanup_sighand; 1441 retval = copy_mm(clone_flags, p); 1442 if (retval) 1443 goto bad_fork_cleanup_signal; 1444 retval = copy_namespaces(clone_flags, p); 1445 if (retval) 1446 goto bad_fork_cleanup_mm; 1447 retval = copy_io(clone_flags, p); 1448 if (retval) 1449 goto bad_fork_cleanup_namespaces; 1450 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1451 if (retval) 1452 goto bad_fork_cleanup_io; 1453 1454 if (pid != &init_struct_pid) { 1455 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1456 if (IS_ERR(pid)) { 1457 retval = PTR_ERR(pid); 1458 goto bad_fork_cleanup_io; 1459 } 1460 } 1461 1462 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1463 /* 1464 * Clear TID on mm_release()? 1465 */ 1466 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1467#ifdef CONFIG_BLOCK 1468 p->plug = NULL; 1469#endif 1470#ifdef CONFIG_FUTEX 1471 p->robust_list = NULL; 1472#ifdef CONFIG_COMPAT 1473 p->compat_robust_list = NULL; 1474#endif 1475 INIT_LIST_HEAD(&p->pi_state_list); 1476 p->pi_state_cache = NULL; 1477#endif 1478 /* 1479 * sigaltstack should be cleared when sharing the same VM 1480 */ 1481 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1482 p->sas_ss_sp = p->sas_ss_size = 0; 1483 1484 /* 1485 * Syscall tracing and stepping should be turned off in the 1486 * child regardless of CLONE_PTRACE. 1487 */ 1488 user_disable_single_step(p); 1489 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1490#ifdef TIF_SYSCALL_EMU 1491 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1492#endif 1493 clear_all_latency_tracing(p); 1494 1495 /* ok, now we should be set up.. */ 1496 p->pid = pid_nr(pid); 1497 if (clone_flags & CLONE_THREAD) { 1498 p->exit_signal = -1; 1499 p->group_leader = current->group_leader; 1500 p->tgid = current->tgid; 1501 } else { 1502 if (clone_flags & CLONE_PARENT) 1503 p->exit_signal = current->group_leader->exit_signal; 1504 else 1505 p->exit_signal = (clone_flags & CSIGNAL); 1506 p->group_leader = p; 1507 p->tgid = p->pid; 1508 } 1509 1510 p->nr_dirtied = 0; 1511 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1512 p->dirty_paused_when = 0; 1513 1514 p->pdeath_signal = 0; 1515 INIT_LIST_HEAD(&p->thread_group); 1516 p->task_works = NULL; 1517 1518 /* 1519 * Make it visible to the rest of the system, but dont wake it up yet. 1520 * Need tasklist lock for parent etc handling! 1521 */ 1522 write_lock_irq(&tasklist_lock); 1523 1524 /* CLONE_PARENT re-uses the old parent */ 1525 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1526 p->real_parent = current->real_parent; 1527 p->parent_exec_id = current->parent_exec_id; 1528 } else { 1529 p->real_parent = current; 1530 p->parent_exec_id = current->self_exec_id; 1531 } 1532 1533 spin_lock(¤t->sighand->siglock); 1534 1535 /* 1536 * Copy seccomp details explicitly here, in case they were changed 1537 * before holding sighand lock. 1538 */ 1539 copy_seccomp(p); 1540 1541 /* 1542 * Process group and session signals need to be delivered to just the 1543 * parent before the fork or both the parent and the child after the 1544 * fork. Restart if a signal comes in before we add the new process to 1545 * it's process group. 1546 * A fatal signal pending means that current will exit, so the new 1547 * thread can't slip out of an OOM kill (or normal SIGKILL). 1548 */ 1549 recalc_sigpending(); 1550 if (signal_pending(current)) { 1551 spin_unlock(¤t->sighand->siglock); 1552 write_unlock_irq(&tasklist_lock); 1553 retval = -ERESTARTNOINTR; 1554 goto bad_fork_free_pid; 1555 } 1556 1557 if (likely(p->pid)) { 1558 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1559 1560 init_task_pid(p, PIDTYPE_PID, pid); 1561 if (thread_group_leader(p)) { 1562 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1563 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1564 1565 if (is_child_reaper(pid)) { 1566 ns_of_pid(pid)->child_reaper = p; 1567 p->signal->flags |= SIGNAL_UNKILLABLE; 1568 } 1569 1570 p->signal->leader_pid = pid; 1571 p->signal->tty = tty_kref_get(current->signal->tty); 1572 list_add_tail(&p->sibling, &p->real_parent->children); 1573 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1574 attach_pid(p, PIDTYPE_PGID); 1575 attach_pid(p, PIDTYPE_SID); 1576 __this_cpu_inc(process_counts); 1577 } else { 1578 current->signal->nr_threads++; 1579 atomic_inc(¤t->signal->live); 1580 atomic_inc(¤t->signal->sigcnt); 1581 list_add_tail_rcu(&p->thread_group, 1582 &p->group_leader->thread_group); 1583 list_add_tail_rcu(&p->thread_node, 1584 &p->signal->thread_head); 1585 } 1586 attach_pid(p, PIDTYPE_PID); 1587 nr_threads++; 1588 } 1589 1590 total_forks++; 1591 spin_unlock(¤t->sighand->siglock); 1592 syscall_tracepoint_update(p); 1593 write_unlock_irq(&tasklist_lock); 1594 1595 proc_fork_connector(p); 1596 cgroup_post_fork(p); 1597 if (clone_flags & CLONE_THREAD) 1598 threadgroup_change_end(current); 1599 perf_event_fork(p); 1600 1601 trace_task_newtask(p, clone_flags); 1602 uprobe_copy_process(p, clone_flags); 1603 1604 return p; 1605 1606bad_fork_free_pid: 1607 if (pid != &init_struct_pid) 1608 free_pid(pid); 1609bad_fork_cleanup_io: 1610 if (p->io_context) 1611 exit_io_context(p); 1612bad_fork_cleanup_namespaces: 1613 exit_task_namespaces(p); 1614bad_fork_cleanup_mm: 1615 if (p->mm) 1616 mmput(p->mm); 1617bad_fork_cleanup_signal: 1618 if (!(clone_flags & CLONE_THREAD)) 1619 free_signal_struct(p->signal); 1620bad_fork_cleanup_sighand: 1621 __cleanup_sighand(p->sighand); 1622bad_fork_cleanup_fs: 1623 exit_fs(p); /* blocking */ 1624bad_fork_cleanup_files: 1625 exit_files(p); /* blocking */ 1626bad_fork_cleanup_semundo: 1627 exit_sem(p); 1628bad_fork_cleanup_audit: 1629 audit_free(p); 1630bad_fork_cleanup_perf: 1631 perf_event_free_task(p); 1632bad_fork_cleanup_policy: 1633#ifdef CONFIG_NUMA 1634 mpol_put(p->mempolicy); 1635bad_fork_cleanup_threadgroup_lock: 1636#endif 1637 if (clone_flags & CLONE_THREAD) 1638 threadgroup_change_end(current); 1639 delayacct_tsk_free(p); 1640bad_fork_cleanup_count: 1641 atomic_dec(&p->cred->user->processes); 1642 exit_creds(p); 1643bad_fork_free: 1644 free_task(p); 1645fork_out: 1646 return ERR_PTR(retval); 1647} 1648 1649static inline void init_idle_pids(struct pid_link *links) 1650{ 1651 enum pid_type type; 1652 1653 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1654 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1655 links[type].pid = &init_struct_pid; 1656 } 1657} 1658 1659struct task_struct *fork_idle(int cpu) 1660{ 1661 struct task_struct *task; 1662 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1663 if (!IS_ERR(task)) { 1664 init_idle_pids(task->pids); 1665 init_idle(task, cpu); 1666 } 1667 1668 return task; 1669} 1670 1671/* 1672 * Ok, this is the main fork-routine. 1673 * 1674 * It copies the process, and if successful kick-starts 1675 * it and waits for it to finish using the VM if required. 1676 */ 1677long do_fork(unsigned long clone_flags, 1678 unsigned long stack_start, 1679 unsigned long stack_size, 1680 int __user *parent_tidptr, 1681 int __user *child_tidptr) 1682{ 1683 struct task_struct *p; 1684 int trace = 0; 1685 long nr; 1686 1687 /* 1688 * Determine whether and which event to report to ptracer. When 1689 * called from kernel_thread or CLONE_UNTRACED is explicitly 1690 * requested, no event is reported; otherwise, report if the event 1691 * for the type of forking is enabled. 1692 */ 1693 if (!(clone_flags & CLONE_UNTRACED)) { 1694 if (clone_flags & CLONE_VFORK) 1695 trace = PTRACE_EVENT_VFORK; 1696 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1697 trace = PTRACE_EVENT_CLONE; 1698 else 1699 trace = PTRACE_EVENT_FORK; 1700 1701 if (likely(!ptrace_event_enabled(current, trace))) 1702 trace = 0; 1703 } 1704 1705 p = copy_process(clone_flags, stack_start, stack_size, 1706 child_tidptr, NULL, trace); 1707 /* 1708 * Do this prior waking up the new thread - the thread pointer 1709 * might get invalid after that point, if the thread exits quickly. 1710 */ 1711 if (!IS_ERR(p)) { 1712 struct completion vfork; 1713 struct pid *pid; 1714 1715 trace_sched_process_fork(current, p); 1716 1717 pid = get_task_pid(p, PIDTYPE_PID); 1718 nr = pid_vnr(pid); 1719 1720 if (clone_flags & CLONE_PARENT_SETTID) 1721 put_user(nr, parent_tidptr); 1722 1723 if (clone_flags & CLONE_VFORK) { 1724 p->vfork_done = &vfork; 1725 init_completion(&vfork); 1726 get_task_struct(p); 1727 } 1728 1729 wake_up_new_task(p); 1730 1731 /* forking complete and child started to run, tell ptracer */ 1732 if (unlikely(trace)) 1733 ptrace_event_pid(trace, pid); 1734 1735 if (clone_flags & CLONE_VFORK) { 1736 if (!wait_for_vfork_done(p, &vfork)) 1737 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 1738 } 1739 1740 put_pid(pid); 1741 } else { 1742 nr = PTR_ERR(p); 1743 } 1744 return nr; 1745} 1746 1747/* 1748 * Create a kernel thread. 1749 */ 1750pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1751{ 1752 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1753 (unsigned long)arg, NULL, NULL); 1754} 1755 1756#ifdef __ARCH_WANT_SYS_FORK 1757SYSCALL_DEFINE0(fork) 1758{ 1759#ifdef CONFIG_MMU 1760 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1761#else 1762 /* can not support in nommu mode */ 1763 return -EINVAL; 1764#endif 1765} 1766#endif 1767 1768#ifdef __ARCH_WANT_SYS_VFORK 1769SYSCALL_DEFINE0(vfork) 1770{ 1771 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1772 0, NULL, NULL); 1773} 1774#endif 1775 1776#ifdef __ARCH_WANT_SYS_CLONE 1777#ifdef CONFIG_CLONE_BACKWARDS 1778SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1779 int __user *, parent_tidptr, 1780 int, tls_val, 1781 int __user *, child_tidptr) 1782#elif defined(CONFIG_CLONE_BACKWARDS2) 1783SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1784 int __user *, parent_tidptr, 1785 int __user *, child_tidptr, 1786 int, tls_val) 1787#elif defined(CONFIG_CLONE_BACKWARDS3) 1788SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1789 int, stack_size, 1790 int __user *, parent_tidptr, 1791 int __user *, child_tidptr, 1792 int, tls_val) 1793#else 1794SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1795 int __user *, parent_tidptr, 1796 int __user *, child_tidptr, 1797 int, tls_val) 1798#endif 1799{ 1800 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr); 1801} 1802#endif 1803 1804#ifndef ARCH_MIN_MMSTRUCT_ALIGN 1805#define ARCH_MIN_MMSTRUCT_ALIGN 0 1806#endif 1807 1808static void sighand_ctor(void *data) 1809{ 1810 struct sighand_struct *sighand = data; 1811 1812 spin_lock_init(&sighand->siglock); 1813 init_waitqueue_head(&sighand->signalfd_wqh); 1814} 1815 1816void __init proc_caches_init(void) 1817{ 1818 sighand_cachep = kmem_cache_create("sighand_cache", 1819 sizeof(struct sighand_struct), 0, 1820 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1821 SLAB_NOTRACK, sighand_ctor); 1822 signal_cachep = kmem_cache_create("signal_cache", 1823 sizeof(struct signal_struct), 0, 1824 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1825 files_cachep = kmem_cache_create("files_cache", 1826 sizeof(struct files_struct), 0, 1827 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1828 fs_cachep = kmem_cache_create("fs_cache", 1829 sizeof(struct fs_struct), 0, 1830 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1831 /* 1832 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1833 * whole struct cpumask for the OFFSTACK case. We could change 1834 * this to *only* allocate as much of it as required by the 1835 * maximum number of CPU's we can ever have. The cpumask_allocation 1836 * is at the end of the structure, exactly for that reason. 1837 */ 1838 mm_cachep = kmem_cache_create("mm_struct", 1839 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1840 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1841 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1842 mmap_init(); 1843 nsproxy_cache_init(); 1844} 1845 1846/* 1847 * Check constraints on flags passed to the unshare system call. 1848 */ 1849static int check_unshare_flags(unsigned long unshare_flags) 1850{ 1851 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1852 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1853 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1854 CLONE_NEWUSER|CLONE_NEWPID)) 1855 return -EINVAL; 1856 /* 1857 * Not implemented, but pretend it works if there is nothing 1858 * to unshare. Note that unsharing the address space or the 1859 * signal handlers also need to unshare the signal queues (aka 1860 * CLONE_THREAD). 1861 */ 1862 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1863 if (!thread_group_empty(current)) 1864 return -EINVAL; 1865 } 1866 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 1867 if (atomic_read(¤t->sighand->count) > 1) 1868 return -EINVAL; 1869 } 1870 if (unshare_flags & CLONE_VM) { 1871 if (!current_is_single_threaded()) 1872 return -EINVAL; 1873 } 1874 1875 return 0; 1876} 1877 1878/* 1879 * Unshare the filesystem structure if it is being shared 1880 */ 1881static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1882{ 1883 struct fs_struct *fs = current->fs; 1884 1885 if (!(unshare_flags & CLONE_FS) || !fs) 1886 return 0; 1887 1888 /* don't need lock here; in the worst case we'll do useless copy */ 1889 if (fs->users == 1) 1890 return 0; 1891 1892 *new_fsp = copy_fs_struct(fs); 1893 if (!*new_fsp) 1894 return -ENOMEM; 1895 1896 return 0; 1897} 1898 1899/* 1900 * Unshare file descriptor table if it is being shared 1901 */ 1902static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1903{ 1904 struct files_struct *fd = current->files; 1905 int error = 0; 1906 1907 if ((unshare_flags & CLONE_FILES) && 1908 (fd && atomic_read(&fd->count) > 1)) { 1909 *new_fdp = dup_fd(fd, &error); 1910 if (!*new_fdp) 1911 return error; 1912 } 1913 1914 return 0; 1915} 1916 1917/* 1918 * unshare allows a process to 'unshare' part of the process 1919 * context which was originally shared using clone. copy_* 1920 * functions used by do_fork() cannot be used here directly 1921 * because they modify an inactive task_struct that is being 1922 * constructed. Here we are modifying the current, active, 1923 * task_struct. 1924 */ 1925SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1926{ 1927 struct fs_struct *fs, *new_fs = NULL; 1928 struct files_struct *fd, *new_fd = NULL; 1929 struct cred *new_cred = NULL; 1930 struct nsproxy *new_nsproxy = NULL; 1931 int do_sysvsem = 0; 1932 int err; 1933 1934 /* 1935 * If unsharing a user namespace must also unshare the thread. 1936 */ 1937 if (unshare_flags & CLONE_NEWUSER) 1938 unshare_flags |= CLONE_THREAD | CLONE_FS; 1939 /* 1940 * If unsharing vm, must also unshare signal handlers. 1941 */ 1942 if (unshare_flags & CLONE_VM) 1943 unshare_flags |= CLONE_SIGHAND; 1944 /* 1945 * If unsharing a signal handlers, must also unshare the signal queues. 1946 */ 1947 if (unshare_flags & CLONE_SIGHAND) 1948 unshare_flags |= CLONE_THREAD; 1949 /* 1950 * If unsharing namespace, must also unshare filesystem information. 1951 */ 1952 if (unshare_flags & CLONE_NEWNS) 1953 unshare_flags |= CLONE_FS; 1954 1955 err = check_unshare_flags(unshare_flags); 1956 if (err) 1957 goto bad_unshare_out; 1958 /* 1959 * CLONE_NEWIPC must also detach from the undolist: after switching 1960 * to a new ipc namespace, the semaphore arrays from the old 1961 * namespace are unreachable. 1962 */ 1963 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1964 do_sysvsem = 1; 1965 err = unshare_fs(unshare_flags, &new_fs); 1966 if (err) 1967 goto bad_unshare_out; 1968 err = unshare_fd(unshare_flags, &new_fd); 1969 if (err) 1970 goto bad_unshare_cleanup_fs; 1971 err = unshare_userns(unshare_flags, &new_cred); 1972 if (err) 1973 goto bad_unshare_cleanup_fd; 1974 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1975 new_cred, new_fs); 1976 if (err) 1977 goto bad_unshare_cleanup_cred; 1978 1979 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 1980 if (do_sysvsem) { 1981 /* 1982 * CLONE_SYSVSEM is equivalent to sys_exit(). 1983 */ 1984 exit_sem(current); 1985 } 1986 if (unshare_flags & CLONE_NEWIPC) { 1987 /* Orphan segments in old ns (see sem above). */ 1988 exit_shm(current); 1989 shm_init_task(current); 1990 } 1991 1992 if (new_nsproxy) 1993 switch_task_namespaces(current, new_nsproxy); 1994 1995 task_lock(current); 1996 1997 if (new_fs) { 1998 fs = current->fs; 1999 spin_lock(&fs->lock); 2000 current->fs = new_fs; 2001 if (--fs->users) 2002 new_fs = NULL; 2003 else 2004 new_fs = fs; 2005 spin_unlock(&fs->lock); 2006 } 2007 2008 if (new_fd) { 2009 fd = current->files; 2010 current->files = new_fd; 2011 new_fd = fd; 2012 } 2013 2014 task_unlock(current); 2015 2016 if (new_cred) { 2017 /* Install the new user namespace */ 2018 commit_creds(new_cred); 2019 new_cred = NULL; 2020 } 2021 } 2022 2023bad_unshare_cleanup_cred: 2024 if (new_cred) 2025 put_cred(new_cred); 2026bad_unshare_cleanup_fd: 2027 if (new_fd) 2028 put_files_struct(new_fd); 2029 2030bad_unshare_cleanup_fs: 2031 if (new_fs) 2032 free_fs_struct(new_fs); 2033 2034bad_unshare_out: 2035 return err; 2036} 2037 2038/* 2039 * Helper to unshare the files of the current task. 2040 * We don't want to expose copy_files internals to 2041 * the exec layer of the kernel. 2042 */ 2043 2044int unshare_files(struct files_struct **displaced) 2045{ 2046 struct task_struct *task = current; 2047 struct files_struct *copy = NULL; 2048 int error; 2049 2050 error = unshare_fd(CLONE_FILES, ©); 2051 if (error || !copy) { 2052 *displaced = NULL; 2053 return error; 2054 } 2055 *displaced = task->files; 2056 task_lock(task); 2057 task->files = copy; 2058 task_unlock(task); 2059 return 0; 2060} 2061 2062int sysctl_max_threads(struct ctl_table *table, int write, 2063 void __user *buffer, size_t *lenp, loff_t *ppos) 2064{ 2065 struct ctl_table t; 2066 int ret; 2067 int threads = max_threads; 2068 int min = MIN_THREADS; 2069 int max = MAX_THREADS; 2070 2071 t = *table; 2072 t.data = &threads; 2073 t.extra1 = &min; 2074 t.extra2 = &max; 2075 2076 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2077 if (ret || !write) 2078 return ret; 2079 2080 set_max_threads(threads); 2081 2082 return 0; 2083} 2084